The present invention relates to a receiver having an interferometer, and more particularly, to a fiber optic data receiver having an interferometer to select a synchronization (sync) signal.
In fiber optic local area networks wherein data is transmitted in bursts, clock signal recovery and data synchronization is difficult due to the short duration of the bursts. In particular, if the data is Manchester encoded with the data signal at a frequency f.sub.o, then the sync signal is as a frequency 2f.sub.o. A typical prior art technique for extracting the sync signal is to bandpass filter the received signal at 2f.sub.o, or if a preamble at 2f.sub.o is sent, threshold detect it and use the detected preamble to excite a ringing tank circuit oscillator at 2f.sub.o. In either case, disadvantages include low signal-to-noise ratio (SNR), jitter, distortion due to threshold detection, and loss of at least a portion of the preamble due to time constant effects in a threshold detector, all caused by the short duration of the signal.
It is, therefore, desirable to have a receiver that recovers a sync signal, especially wherein the data signal occurs in bursts, that has a high SNR, low jitter, low distortion and low loss of preamble.